Microsoft's Outlook and Hotmail spam filters went off piste on Wednesday, dumping an avalanche of unwanted bumf in inboxes.

The snafu was resolved by early afternoon, here in Western Europe.

"Some users may be receiving excessive spam mail," read a warning that briefly popped up on Microsoft's Outlook.com service status page. The glitch lasted around 12 hours, during which time the filters failed to hold back tons of offers for dodgy pills, marriage proposals and other crap from people's email accounts.

Microsoft is in the process of migrating its Outlook.com backend over to its Office 365 service but it’s not immediately clear whether or not a snag in this process caused the problem. El Reg pinged Microsoft’s PR folks for comment but we've yet to hear back.

“On a 'normal' day I might get one to two spams through the filters,” said Reg reader Paul, who first alerted us to the problem. “In the past 36 hours I've had more than 80 spams get through.”

Plenty of Hotmail users took to Twitter to complain about a severe junk mail deluge.

I am in Canada at the moment and did recive 2 emails that got through, only to my spam folder, but I flushed them before opening them. You can usually tell just by the headline of the email and hovering your mouse pointer over the sender one will see the true url of the sender, that's enough for me to flush these right away.